Kristian Hogsberg, Red Hat Xorg developer and the key person behind successful projects such as AIGLX, has now started working on a new project called Wayland, a tiny display server and compositing manager.

There's no point in breaking the API. Old stuff will be unused and barely supported, being of almost no cost to the project, and new stuff can be added, heavily-used stuff can be optimized. Thanks to widespread use of toolkits, most apps can seamlessly switch over to using new features without even having to recompile.